1. Field of the Invention
The present invention relates to a straight angle conductor and a method of manufacturing the same, and in particular to a straight angle conductor with a cladding material including a core-sheet material and a conductor-sheet material that sandwiches the core-sheet material.
2. Description of the Related Art
As a solar cell a semiconductor chip has been used in which silicon crystal wafer is grown on a substrate. A connection-lead wire is soldered to a predetermined area (contact area) of a silicon crystal wafer that results from cutting and dividing this semiconductor chip. The power is transmitted (outputted) through the connection-lead wire.
A solder plated layer is usually formed on a surface of a conductor as a part of the connection-lead wire for connection of the conductor with the silicon crystal wafer. As the conductor, for instance, is used a straight angle conductor made of pure copper such as tough pitch copper or oxygen free high conductivity copper, and as the solder plated layer is used Sn—Pb eutectic solder (See, for instance, Japanese Unexamined Patent Publication No. 11-21660). In place of the Sn—Pb eutectic solder, however, there has recently come to study use of a solder which does not contain Pb (Pb free solder) as the solder-plated layer material from a viewpoint of an environment (See, for instance, Japanese Unexamined Patent Publication No. 2002-263880).
Further, a silicon crystal wafer among components included in a solar cell occupies most of material costs, so that a study on how to manufacture a thinner silicon crystal wafer has been made for decrease of manufacturing costs. When the silicon crystal wafer is, however, designed to be thinner, damage in the silicon crystal wafer tends to be produced due to heating process on soldering connection of the connection-lead wire thereto or due to a change in temperature for use in the solar cell. To cope with this problem, there exist increasing demands for a connection-lead wire of a small thermal expansion coefficient and a connection-solder plated layer of a low melting temperature.
As one example of a lead wire having a small thermal expansion coefficient, there is a lead frame formed of a plate or a rod member configured by cladding an INVER (registered trademark) with copper materials (namely, in the form of copper—INVER (registered trademark)—copper) (See, for instance, Japanese Unexamined Patent Publication No. 2002-164560)